The Silver ticket attack is based on crafting a valid TGS for a service once the NTLM hash of service is owned (like the PC account hash). Thus, it is possible to gain access to that service by forging a custom TGS as any user.
In this case, the NTLM hash of a computer account (which is kind of a user account in AD) is owned. Hence, it is possible to craft a ticket in order to get into that machine with administrator privileges through the SMB service. The computer accounts reset their passwords every 30 days by default.
The CIFS service is the one that allows you to access the file system of the victim. You can find other services here: https://adsecurity.org/?page_id=183. For example, you can use the HOST service to create a schtask in a computer. Then you can check if this has worked trying to list the tasks of the victim: schtasks /S <hostname> or you can use the HOST andRPCSS service to execute WMI queries in a computer, test it doing: Get-WmiObject -Class win32_operatingsystem -ComputerName <hostname>
Silver ticket events ID (more stealth than golden ticket):